Taking a 90-minute nap the day of a test or presentation sounds like a ludicrous luxury. But a recent study on the brain's ability to recall facts found that napping at noon could mean a lot more brain power at 6 p.m.

At noon, all the participants were subjected to a rigorous learning task intended to tax the hippocampus, a region of the brain that helps store fact-based memories. Both groups performed at comparable levels.

At 2 p.m., the nap group took a 90-minute siesta while the no-nap group stayed awake. Later that day, at 6 p.m., participants performed a new round of learning exercises. Those who remained awake throughout the day became worse at learning. In contrast, those who napped did markedly better and actually improved in their capacity to learn.

It's not the first time, or the second, that we've seen naps and memory functions tied together. But each study has its participants trying out slightly different tasks, and this study suggests that if you're trying to cram in facts you need to recall later, a same-day nap before your last-minute cram might be more helpful than powering through your day with nervous energy.

It also suggests that the brain uses a sleep state between light sleep and deep REM phases to pull a kind of soft reset on the brain's memory recall powers, so a fear that you can't let yourself sleep "too deeply" in a nap seems unfounded.